Plunged into negotiations with other parties off the back of an election result where the party lost seats, you might expect the Liberal Democrats to be racked by internal dissent and argument. Instead, the mood at the grassroots is remarkably unified.

Pensive and tense, certainly, as the latest news of the negotiations rolls across the TV screens and blogs, but that comes from knowing what a once-in-a-generation opportunity is being played out in rooms around Westminster.

Many have an instinctive preference or aversion to one of the other main parties, but what they all have in common is a commitment to the Liberal Democrats. Those in principle who would never touch party X with a bargepole are greatly outnumbered by those who don't mind if it's party X or party Y – as long as there is a good deal for Liberal Democrat policies in the process. In part that is born of seeing the experiences in devolved governments and local councils around the UK. There is no one magic pairing that has always been the best choice, and no one cursed pairing that has always been the worst choice. It all depends on the circumstances and what can be agreed.

It's on electoral reform that agreement is hardest to envisage – but electoral reform is central to why many members, and particularly activists, chose to join the Liberal Democrats rather than another party.

The motivation isn't an abstract desire for a mathematical neatness between the number of votes a party gets and the number of seats, but rather about changing the type of politics we have. Our current system not only allows a party to win a small share of the votes and then get absolute executive power, it also means that many seats simply never change hands. In the 40 years running up to last Thursday, half the parliamentary seats never changed hands between parties. Looking at the results, it's likely that number won't have been changed very much, even after the gains and loses this time around.

It's a shocking statistic – and means that for far too many MPs, it doesn't really matter what they get up to. They can just carry on getting re-elected for as long as they want. The complacency, bad habits and poor government which flow from that is why electoral reform is such a gut issue for so many Liberal Democrats. It's not about academic debates on the features of different electoral formulas; it's about the gritty realities of taking power away from the political establishment and giving it to voters.

It therefore was hardly a surprise that a poll of 347 party members by Liberal Democrat Voice over Sunday and Monday found 80% saying that significant progress on changing the electoral system is a deal-breaker. As one member put it to me – we didn't win the election, so of course we don't get to have all of our manifesto. But we need to push the other parties as hard as we can to get as much as we can on electoral reform.

The party's negotiating team is winning many plaudits for doing just that. The big question is whether a promise to hold a referendum on AV is the most that can be achieved as part of an otherwise plausible and durable agreement – and if it is, whether or not that would be enough. Liberal Democrat grassroots members I've talked to would dearly love there to be more on offer but, of course, it takes two sides to agree a deal.